[BUG] /fast doesnt work in Cursor/VScode Claude extension

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

I type /fast in Claude extension in Cursor and instead of enabling fast mode it opens the terminal in cursor and enters: claude /fast. (that shows an error, but it shouldn't be doing anything in the terminal anyway). I have the extension model set to Opus 4.6

<img width="586" height="167" alt="Image" src="https://github.com/user-attachments/assets/f9023bb3-7b47-47c7-9cf6-a638684b2968" />

<img width="1049" height="48" alt="Image" src="https://github.com/user-attachments/assets/26a1fbba-aa8b-4318-8ac5-3b20550497e6" />

What Should Happen?

It should enable fast mode in Claude extension

Error Messages/Logs

Steps to Reproduce

in Claude extension type /fast

Claude Model

Opus

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.42

Platform

Other

Operating System

Windows

Terminal/Shell

Cursor

Additional Information

_No response_